The present invention relates to transmission system fault measurements, and more particularly to a transient distance to fault (DTF) measurement using per frequency triggered I and Q data.
Many users have to deal with the problem of intermittent problems in transmission systems, such as loose or corroded connectors, antenna flaws, etc. For example where cables are exposed to environmental conditions, such as antenna cables exposed to wind and rain, loose or corroded connectors may result in intermittent loss or degradation of signal in the cables. This is particularly irritating to customers who rely upon a constant signal being carried by the cables, such as wireless subscribers, television viewers, radio listeners, etc.
The normal course of action to deal with such intermittent problems is to connect a distance to fault (DTF) or time domain reflectometer (TDR) to the transmission path and then shake the transmission cable or in some way cause the transient or intermittent event to occur in the transmission system. It is difficult to detect transients on DTF or time domain equipment because the transient event is masked by all of the non-transient data.
What is desired is a method for improving the ability to detect and identify distance to transient errors in a transmission system by using frequency domain equipment.
Accordingly the present invention provides a transient distance to fault measurement using per frequency triggered I and Q data. Initially a result set of data entries, one for each discrete frequency in a specified frequency range, is filled with zeros and an initial acquisition set of per frequency I and Q data from a transmission system is used to fill a reference set of data entries. Subsequent acquisitions of per frequency data sets are used to fill a current set of data entries. Between each acquisition of data sets for the current set a comparison is made, entry by entry, between the current set and the reference set, and the data from the current set is used to update the entry in the result set when the difference exceeds a specified tolerance. The updating may be a direct copy of the entry data from the current set to the result set, an accumulation of the entry data with the data in the result set with or without weighting, or a replacement of the entry data in the result set when the current set entry data exceeds the result set entry data. When all of the entries of the current set have been compared with the reference set and the results processed for the result set, the result set is displayed by performing an inverse Fourier transform on the result set to provide a distance to fault display in the time domain. The data acquisitions occur while the transmission system is being perturbed to stimulate the transient event.
The objects, advantages and other novel features of the present invention are apparent from the following detailed description when read in conjunction with the appended claims and attached drawing.